Northstar Engines and System Technical Discussion Discussion, Main thread pulled out in Cadillac Engine Technical Discussion; I Time-Serted all of head bolt threads even though they looked perfect, and I am glade I did. Because this ...

Main thread pulled out

I Time-Serted all of head bolt threads even though they looked perfect, and I am glade I did. Because this afternoon I was assembling the engine and I had a main thread fail and only under a very light load.

This engine (94 N*) had one main thread that looked dull and a little ruff, several people assurred me - the mains seldom if ever fail - don't even worry about them.

Well I did worry at first but with that assurance I felt better - But I wanted to test it anyway at least a little and ran a bolt down that thread and ones near it and tighten it up enough just to test it to see if it was still feeling smooth, good and solid. I did that a couple weeks ago. The bolt went in smoothly, tightened solidly and came out just as smoothly - OK great, they really do know what they are taking about and I stopped worrying.

But after cleaning the engine extremely well and having the engine apart for several weeks for parts I was finally assembling the crank, pistons, rods and the half case with a new oil manifold - and that same main thread now didn't want to take a bolt very easily. I inspected it, it was empty and clean. So I tried a different bolt which made no difference. It was tight, much tighter and ruffer going than weeks before and much more than all the other main's threads, and then it failed with less than half the force than I had put on it before and far than what it was going to have to handle. Some of the threads came out with the bolt threads, they were ruff crumbly and weak. It was fine before, what happend? I was more than a little confussed and ticked off.

Why did it fail so easily now, when it performed so much better when I had tested it? And what about the rest of the main threads? One possible answer comes from when I worked in an aircraft engine shop. They had a big solvent dip tank, it was at least 4 feet high, 4 feet wide and 10 feet long and the whole torn down engine was carfully allowed to saok in it. But only for a few hours (I can't remember how many) but it was a very big deal if any didn't get the engine out and washer it off before going home at night. If the parts were left to long in the tank the solvent(s) would actually soften and weaken the aluminum.

After removal from the solvent bath each part had to be carefull sprayed and cleaned off with water (I think it nutralized it), then each was blown off with air and then cleaned and sprayed off carefully with toluene (which evaporates quickly) to get make sure all the water and solvent were off and out of every nook, crany and hole.

For the last two weeks I have clean every part of this N* engine several times with carb cleaner (toluene and other fast evaporizing solvens) but made sure to keep all the thread holes clean of oil and didn't let the solvent sit in the hole for more than a few minutes (remembering my aircraft shop experience). But in between the time that I tested that main thread and the time of assembly something had changed those threads, they were different.

I think the already weak, dull and ruff thread absorbed more of the solvents and were more effected by them than the other threads were. It oxidized, softened, expanded and changed in both size and shape - and it got much weaker.

Now look what is running through my head. I have an engine cleaned to the bone, with pretty new parts and with all the head bolt threads Time-Serted and with one bad main bearing thread standing in my way. And here I sit with a perfectly good Time-sert head bolt kit. Why couldn't I use it on the the mains? I took a good look at the location on the engine and there appears to be plenty of material there and a head bolt almost fits in the hole already! I would have to get the right length bolt and adjust for the change of depth on the drill bit and tap and wouldn't have the benefit of the jig unless I drill a hole in it to hold it in place or clamped in some other way but why wouldn't this work and work well? The area is already proven to be thick enough to handle a Time-Sert as there is a spical N* kit to do so with - so there is at least enough extra space and material for handle a M10 sert and there appears to be much more. It would be going from a M10 to M11, both have a 1.5 pitch so would there be a difference in torque? How much? or just the different spring rate of the bolt? It's to bad the factory didn't use the same size in both location, I am sure they had their reasons, but I have mine too, several hundred dollars and a nother week of down time as I would have to wait for the main kit to arrive and then try to make the time to work on it. I already took this thursday and friday off to get it all done this weekend.

Hay I am getting serious about this - Has anyone tried up sizing and repairing a main thread with a M11 Time-Sert for the heads? Why couldn't it work - there must be a reason(s). But what?

Re: Main thread pulled out

Myself I don’t think I would try using the larger time-sert and M11 bolt, there are just too many unknowns to deal with. If you are like me every time you stand on it you would wonder if the main bearing bolt changes you made were getting ready to come back and haunt you.
Just a thought but what if you called time-sert to inquire into the purchase of one M10 main bearing time-sert and the corresponding tap? Another forum member Pjs has installed the main bearing time-serts and posted pictures of the job so maybe he would be willing to check the tap size that came with the main bearing kit and see if it is a standard tap size that could be purchased locally and if so that would save you some money. I’m sure you could come up with the correct drill bit to work with the time-sert tap the only problem would be the machining of the ledge to receive the stop shoulder of the time-sert. Maybe if you measured the time-sert shoulder O.D. first then drilled a 1/8” deep recess using the top thread as the starting point utilizing one drill size larger than the shoulder O.D. and then come back with the correct drill for the time-sert tap and drill just a little deeper than the overall length of the time-sert. You would need to make your own drill guide or centering plate. As to installing the insert, apply some of the insert driver oil onto the main bearing bolt, start the time-sert on the bolt then apply the loctite 266 (from the head bolt time-sert kit) to the O.D. of the time-sert then run it in. You may need to cut a piece of pipe to make a spacer sleeve to slide on the bolt between the time-sert and the bolt head to allow the insert to be fully installed without bottoming the bolt in the hole, just a thought. The trick to the whole job would be maintaining a drill position that is centered in the hole and at 90 degrees to the block surface all the while controlling the drilling depth. If you could pull this off it would save you a ton of money and you could still use the correct torque specification for the main bolts. Like I said just a thought. Good luck..

Re: Main thread pulled out

I like the way you think Haymaker, there is more than one good way to skin a cat I also have the same concerns.

The trick to the whole job would be maintaining a drill position that is centered in the hole and at 90 degrees to the block surface all the while controlling the drilling depth. If you could pull this off it would save you a ton of money and you could still use the correct torque specification for the main bolts. Like I said just a thought. Good luck..

That part I don't see as too much of a problem with as it is a predrilled hole and I could use self guiding reamers in steps to enlarge the hole until the final cut.

One point I didn't mention which is obvious to anyone stuck at this point of assembly and then strepping out a main bolt, is - I don't want to open up the halfcase again, everything is clean and nicely sealed. I called Time-Sert to see if the N* main repair kit requires that you take half case off just like you have to remove the heads to use the Time-Sert head kit (I assumed it did). The tech heads were gone until monday but I had the nice receptionist measure the length of the drill bit (5 inches total, the same length as the M10 bolt but not the head) so it is too short even with the plate and guide removed. I had her read the instruction and it sounded identical to the head instuctions. So to make the repair with the the main kit you do have to remove the half case. And that is an important point, not the most important consideration to be sure, but still. So the M10 N* main thread kit won't reach without removing the half case....... hummmmmm.......

But guess what is long enough.... right, the head bolt tools (except the Sert driver), by full inch.

So back to the question can the block handle the M11 Time-sert in that part of the block for the main? The area is exactly 1.00 in each of the main that I could measure (the ones in the middle of the engine) the ones at the front and rear could be different but in the diagram in the manual they appear too have the same thickness. The nice thing is the one that failed is not at the front or back but in one I could measure. The original main bolt had an OD of 0.376 so the threads in the block would only be slightly larger than that. A M10 Time-Sert has a thread OD of 0.474 The OD of the M11 sert thread is 0.503 and the shelf is 0.525 so that will leave almost 1/4 inch of material on both side of the M11 Time-Sert threads - so basically it looks like a M11 head sert has an OD about the OD size of a M10 Big-Sert if they made one.

So from at least that concern it looks like a go. From the concern are the tools long enough to get the job done so I don't have to remove the halfcase - it looks like a go. The Time-Sert tech won't be back until monday, if I have order something and wait for to get here time I get and find time to work on it after that it will be next weekend, so it's go. Could the M11 be tightened to match the M10 clamping force - I think I will need or at least want to also do a matching M11 Time-Sert on the other side of that bearing to make sure it equal under all condition - so that is also a go. Is Loose Screw crazy enough to try it - it looks clearly like a go. Do I have any extra Time-Serts? YES! plenty ---------- it's a go!

Re: Main thread pulled out

What torque/torque-angle spec. do you plan to use on the M11 bolts? I know applying the torque/torque-angle spec. for the M10 bolt to the M11 bolt will not achieve the proper bolt stretch to insure the M11 bolt will remain tight. Then on the other hand if you tighten the M11 using the head bolt spec. of 22lb/ft-60-60-60 degrees will the area around the new time-sert withstand the added static load? Which 11mm bolts do you plan to use? Just a thought but the effective length of the old head bolt is 5.490 and has a threaded length of 1.854 so in theory you could cut the bottom 0.490 of threads from the old head bolt and have the correct usable bolt length with some unused threads left over (if I read your post correctly you stated the main bolt length to be 5”). Do you plan to loctite the M11 bolts? It looks as though you would be removing an additional 0.015 from each surrounding wall using the 11mm time-serts compared to the 10mm time-serts (not really all that much but what do I know the extra 0.015 maybe enough to cause a failure). This is all very interesting. Let me know how it all turns out.

Re: Main thread pulled out

All good points haymaker I was looking at all those extra threads on the head bolts and cutting off the end seem the obvious good answer but would result in less spring in that bolt and in my thinking it will all ready be more rigid than M10 bolt at the same tightness because of it's bigger diameter. I am assuming they are hardened to the same grade but that could be different too.

As for what spec to use to tighten the M11 - that is the question I would not use the head bolt spec you mention is 22lb/ft-60-60-60 degrees but the manual says 22lb/ft +90 +90 But I read in some other post that it is now 30 lb/ft +70 +60 +60 = total 190 I need some one Like Bbob to clear this up on what the latest spec is for the 94 N* head bolts. and what is the latest for the mains.

If I can't get the answer from the many more knowledgable and experinced people here I will use the factory manual spec for the M10 main main bolt on the M11 they have the same pitch (1.5) so 65 degrees of rotation should result in the same pull in of the bolt. But as I said I would think the it would be less springy and the bolt would streach just a less as a result - resulting a higher clamping force. The goal is to match the clamping force of the M10 so even if the Time-Sert and surround materail had no problems staying in and handle the head bolt tightening spec - that would be way too much. The mains according the the manual only get 15 lb/ft +65 degrees I bet that has been up dated and is higher now. I f nothing else I would use that but certainly not exceed it on the M11 but probably knock off 5 degrees to adjust for less streach.

Does some one please have the latesttightening specs for both the head bolts and for the mains?

I am sure some place (in an engineering book) there are equalivance charts or programs that would tell what rotation would be equal for many different sizes, length and grades of bolts. Some body help here please!

Re: Main thread pulled out

Originally Posted by haymaker

You do realize that if the 11mm time-sert installation or application fails your N* block will in all probability become a very large doorstop.

Yes scary it's it... or get it welded, not very likely becuase the two case are bolted and then machined together and welding would mess it up and it would have to be remachined they do that on aircraft engine but on a N* nobody is setup to do that.

On the other hand this may result in a new reliable and common repair method for the mains.

Re: Main thread pulled out

[QUOTE]One point I didn't mention which is obvious to anyone stuck at this point of assembly and then strepping out a main bolt, is - I don't want to open up the halfcase again, everything is clean and nicely sealed. I called Time-Sert to see if the N* main repair kit requires that you take half case off just like you have to remove the heads to use the Time-Sert head kit (I assumed it did).

I feel your pain dude. I had the to remove the bolts a couple times because of some confusion over the updated oil manifold and when I went to torque them for the 3rd time, the second bolt threads failed and pulled right out of the block. I hate to tell you this, but you DO have to pull the case apart, as well as pulling the crank out too as the drill plate won't fit around the crank counterweights. After reading your's and Haymakers posts, I think the biggest problem you will run into without the right kit is getting the step into the bored hole that accepts the ridge around the timesert. I have the main kit that I can loan you and all you'll need to get is some inserts.

Here is the thread that I posted the process pics in *note the shot of the step in the clean bored hole*.

Re: Main thread pulled out

I feel your pain dude. I had the to remove the bolts a couple times because of some confusion over the updated oil manifold and when I went to torque them for the 3rd time, the second bolt threads failed and pulled right out of the block. I hate to tell you this, but you DO have to pull the case apart, as well as pulling the crank out too as the drill plate won't fit around the crank counterweights. After reading your's and Haymakers posts, I think the biggest problem you will run into without the right kit is getting the step into the bored hole that accepts the ridge around the timesert. I have the main kit that I can loan you and all you'll need to get is some inserts.

Here is the thread that I posted the process pics in *note the shot of the step in the clean bored hole*.

I read your fine instructions before - well done I like how you covered the whole engine like they do a patient's body when they operate.

I have already Time-Serted all of the head bolts two weeks ago.

As for the main thread that ripped out, it was the one the oil pickup tube attaches to. I noticed that even though this engine had the second generation oil manifold plate with the molded in pickup tube seal (second generation has the raised main bolt areas, the thrid are the same thickness all over) it still had the old pickup tube but with no O-ring in it so it probably didn't seal well and the mechanic may of taken that main bolt out a few times and weakened it that way. Changing that bolt to a M11 head bolt or other M11 bolt will eliminate the top stud so the windage must be under the head of the bolts so I will have to use the new windage tray which I was going to use any way but I will need to make a small bracket that will fit on top of in but under the bolt head that I could than attach the oil pickup tube some how. Question - does the new oil pickup tube (without the O-ring grove) fit under the bolt head or does it use the old bolt style and sit on top of the head?

Your observation about the step is well taken, particularly if the process is done with the halfcase still on - the head Time-Serts are long (longer than the main Time-Serts) and careful measuring during the use of the step drill must be taken to make sure the step is cut in the block and not still in the half case, because two bad things would happen 1. the Time-Sert would hold the halfcase on if the step is postioned in the half case. The Sert would be trapped by the lip of the step but also threaded and locktited in to block, you could never get it a part again without drilling out (off) at least the entrapped end of the sert. 2. Recessing the sert helps to prevent cracking - you may have notice all the N* in the block threads do not start at the surface but are recessed, this helps to preven a crack forming at the surface, and protects the thread from being damaged during manufacturing it also prevent any deformation from the threads from interferring with the halfcase and block coming together. A Time sert that would still be in both side of the joint will prevent the case/block from properly coming together during tightening. So you want to get the sert deep enough into the block, but you don't want to go so deep, too deep that you risk come out some place or breaking out some where as the sert binds and wedges it self at the bottom of the hole - there is room but very limited on the front and back of the engine in terms of depth - you can see the thread bosses there. So given that don't go any deeper than getting the top of the sert just below the surface of the block The head sert could be shortened on one end or the other but that would modify one of it's functions and they are coated and it is best not to do anything to effect that protective coating.

But if for some application you had to, you could cut off the starting end and insert the sert, it won't bind as strongly into the metal but it would still be stronger than a Helicoil in my opinion.

I can see if a person installed a Time-Sert and a breakout occured they could as a last ditched emergency repair but a permanet repair - leave the sert in, remove the driver and clean the hole with a solvent and then without getting any on the threads of the sert fill the bottom of the hole will a metal filled epoxy, the slow curing ones are stronger and safer for this application. Coat the threads and the end of the bolt with a release agent (a lite oil, teflon spray or other thin lubricant any of these should work to prevent the epoxy from sticking to it the bolt but still allow air to escape slowly) then run the bolt in VERY VERY slowly and do so a little deeper (at least 1/8 inch) than it will during use. You may need to get a longer bolt to do that or remove a washer if you doing with the hald case or what ever part that the bolt holds down. But you must do it as the bolt must not bottom out when finally tightened. You should see some epoxy push out. If not add more epoxy and clean the bolt well and add more release. Reinstal the bolt and turn it in until you get to the right depth which would be a little extra in. Cean off what has come out. Let the rest cure for a few hours to where it is setup good but not so cured that it is very strong because you want any on the bolt to deform or break off to let the bolt out. Remove the bolt let full cure 48 hours and clean out the hole and the bolt threads with solvent. The epoxy will be force under presure into and out of any cracks, did mention you run tbe bolt in slowly VERY VERY slowly when so see or feel pressure is being developed - give it pleanty of time for the air to leak out frist past the threads and gradually turn the bolt in and force the extra part of the thimble full of epoxy partially out. When done the break out will be sealed and stronger but not as strong obviously as before the break out - but COULD be strong enough depending on how bad and where the break out occured to still make the engine usable.

To prevent break outs always clean the whole one last time and run the tap down all the way one last time to make the Sert has room to expand at the bottom which is does once the driver or bolt is forced through past it's end. The head bolt holes appear extra deep to make manufacturing the threads easier. The holes for the mains thread are also extra deep BUT not enough for the even longer Head Sert that will fo into it. The hole must be drilled even deeper and the Time-set step drill bit can not do that, it can only enlarge a hole it can't make it deeper. You must predrill to the right depth and then use the step drill bit to finish the job, then cut the threads with the timesert tap making sure to get all the way to the bottom of a clean hole. Which should be 3/8 deeper than where the bottom of the Sert will reach, why? Because the tap will not cut perfect ussable threads all the way to the bottom, at the bottom the threads are only partially cut and if you put a sert into those partial threads, when the sert driver goes through the end of the sert and expands it there will be an excessive interferance fit and possible bust out or crack.

Thanks Patrick for the offer of the loan of the Main Time-Sert kit (very generous and kind of you) but it looks like I am going to try using M11 head bolt Time-Sert (which I already have) to fix the main that ripped out. I measured carefully and scratched my head a lot and it looks like it will work and the inventor in me now has to prove out my solution. The right side of my brain is making me do it, and left side can't find the reason it won't work and/or stop me.

Re: Main thread pulled out

Originally Posted by Loose screw

I read your fine instructions before - well done I like how you covered the whole engine like they do a patient's body when they operate.

LOL...I work as a surgical coordinator for 6 neurosurgeons. I just wanted to make sure that I had as much protection against stray metal chips as possible. Although the crank was out, I still had the heads on and the pistons in...my head gaskets are still original.

As for the main thread that ripped out, it was the one the oil pickup tube attaches to. I noticed that even though this engine had the second generation oil manifold plate with the molded in pickup tube seal (second generation has the raised main bolt areas, the third are the same thickness all over) it still had the old pickup tube but with no O-ring in it so it probably didn't seal well and the mechanic may of taken that main bolt out a few times and weakened it that way. Changing that bolt to a M11 head bolt or other M11 bolt will eliminate the top stud so the windage must be under the head of the bolts so I will have to use the new windage tray which I was going to use any way but I will need to make a small bracket that will fit on top of in but under the bolt head that I could than attach the oil pickup tube some how. Question - does the new oil pickup tube (without the O-ring grove) fit under the bolt head or does it use the old bolt style and sit on top of the head?

The new tube (for the molded in seal) bracket still mounts to the stud on top of the inner main bolt.

Thanks Patrick for the offer of the loan of the main Time-Sert kit (very generous and kind) but it looks like I am going to try using M11 head bolt Time-sert (which I already have) to fix the main that ripped out. I measured carefully and scratched my head a lot and it looks like it will work and the inventor in me now has to prove out my solution. The right side of my brain is making me do it, and left side can't find the reason it won't work and/or stop me.

Before you try to do that, might I suggest that you try to tension up the other bolts and see if any others give? When I did the sert installation, I only did 19 out of 20 bolts as one of the holes at the rear main seal looked as though the factory had some sort of insert in the hole already and I didn't think there was enough meat to install the timesert. As luck would have it, it was the last bolt I torqued and of course...it stripped right away. So there I was...having to pull it all apart again, including the crank. After that there is no way I would ever just do one insert. I know it's a lot of work to take it apart, but to be honest I had the whole thing apart including cleaning off the anearobic sealer in less than an hour. My offer still stands for the loan. I would hate to see all the work you've done so far be for naught if your idea doesn't work.

Re: Main thread pulled out

I gave it alot of thought but previously I had read Bbod talk about the factory RTVing the lower end of the engine and that they had the best leak record and the the 2005's are sealed with RTV. I had seen an engine that had the halfcase seal with blue RTV it did not leak there but it had several leaks else where. So I decide to RTV all the lower seals including the halfcase which I did when I put put together and afterwards had the main thread fail. I did a really nice job, I could have taken it a part rather easily as it takes a long time to cure and clean it all off and now that it is cured I could still do that as it would also mean waiting for a main Time-Sert kit.

Oh did I mention I did the deed.

That's right the stripped out main has a head Sert sucessfully installed so does the one on the other side of the bearing. I have also pre-drilled, step-drilled out all of the mains that are closest to the bearings (but I still have to install the Sert in them). I had to leave for work. I have enough head Time serts to do all 20. But I figured the ones closet to the crankshaft are the most stressed so I did those first. Also the four on the front and rear and that are furthest from the crankshaft have the least amount of material around them and at there bottom. They worry me far more than the others.

Patrick - could you please measure on your kit the step drill bit designed for the mains the distance from the top of the step to the bottom of the drill bit. How long is it? Is it shorter than the head step drill bit, and how how long are those main Time-Serts. It may be wise or even necessary to use the serts design for those 4 locations or a shorter M11 sert to reduce the depth of the hole needed.

Re: Main thread pulled out

Update - I woke up a little early this afternoon (I work at night 12 hours) and install edthe remaining 8 Time-Serts in the holes previously pre-drilled then step drilled with Time-Sert's drill bit and thread with their tap. And using a modified head bolt (I used a cheep diamond file to bevel down the last 2 1/2 threads of the bolt to match the end of Time-Serts driver) because the driver is too short to get down the hole with the halfcase and manifold still clamped on.

Oh I forgot to mention, if you do try to repair the main threads with the halfcase still on you need to have the case clamped down good near the repair (and evenly all over to prevent warpage) by only removing no more than halfcase the bolts, Why? to prevent any and all liquids or solids from being forced into the joint and interferring with the finally tightening. So if you strip out one bolt - stop and time sert it before tightening and potentionaly stepping out the bolt next to it, you need it to keep the joint tight and clean throught the repair process. Later you can do the other bolts holes threads.

Another observation there appear to be NO problem doing the remaining 10 threads (famous last words) that are furtherest from the crank shaft. If the factory had added 10 cents more material in the right spots on the front and rear of the engine so the depth of the hole was not such a concern there it would of been helpfull and the head bolt could even be used for the mains in production - as near as I can tell. But they are bigger and more expensive bolts. but still!

Also another idea - sealing the joints in the factory the old way was to install the preformed seals and bolt the joint together. If I understood right from Bbob the lower end of the 2005 are all seal with RTV the process in probably automated were a robot applies RTV in the correct amount at all need location and then the engine is bolted together and allowed to cure for some time.
My idea is to bolt the engine together and then inject the RTV from one end of the engine at several levels or points until in comes out air bubble free at an exit port at the other end of joint or engine. Put a plug in both ends and the engine is seal. For repairs a mechanic could use a grease gun filled with RTV to inject the joint. The nice thing about this is - no mess from the RTV getting sqwished out (and into the inside of the engine it is easy to clean or tear or rub off from the inside the halfcase but why not eliminate that mess and possiblity of contamination to the oil and plugging of the oil pickup tube screen). In injection molding plastic is forced with tons of pressure into every cavity and the only thing that can leak out of the joint is air because the mold is clamped together with tons of pressure. No leaks occure. I don't see why this fast method could be used in sealing and engine, just don't inject with too much pressure its not needed the TRV will flow and let the air out. I would also let a little RTV come out of the furthest point to make sure the seal cavity is full and free of bubbels exiting out a port that could be after wards plugged. The extra RTV could be captured and reused. No wast, no mess, no LEAKS the RTV could even be held in the joint under a certain presure for a short time or when plugging the end, if they used a long plug and it will act as plunger to creat pressure but RTV of course can not be compressed (liquids and solids can not be compressed like gases can unless gasses are mixed in but even then it is the gases that are compressed). But they can exprience pressure. The point is excess RTV under pressure would need to be allowed to leak out perhaps simply through a small whole in the screwed in plugs. like a galley plug with a small control hole. I like this idea - remember you heard it her first.

Re: Main thread pulled out

Originally Posted by Loose screw

Oh did I mention I did the deed.

That's right the stripped out main has a head Sert sucessfully installed so does the one on the other side of the bearing. I have also pre-drilled, step-drilled out all of the mains that are closest to the bearings .

Do I understand you correctly that you have drilled out the main bolt holes for 11 mm bolts and installed 11 mm timeserts...???

You should have waited until I was back in town, dude.... You just scrapped the block for most practical purposes. Sorry to break this to you but the "repair/modification" you made is ill advised.

You REALLY needed to study the oil flow path in the engine carefully to understand it thoroughly before you did what you just did. The main bolt holes in the lower crank case are part of the oil circuit. The pressurized oil is delivered from the filter to the passage that is in the lower crankcase that the oil manifold plate seals off. That passage takes the pressurized oil to each of the inner main bolts just under the head of the main bolts. The pressurized oil flows down the main bolt holes in the lower crankcase to the split line of the block where it feeds the mains. The oil flow path from the oil gallery under the oil distribution plate to each of the mains is the hole for the main bolts. The oil flow area is the difference in the hole size and the bolt size. The hole is bigger than the bolt so there is room for the oil to flow around the OD of the bolt shank. This is why there are 10 mm bolts in the mains...to allow room for the oil flow around the OD of the bolt. By putting larger 11 mm bolts in the holes you have mostly plugged off the oil supply to the mains. This will NOT work. If you continue you will have limited to no oil supply to the mains and rod bearings. Likely you will spin a rod bearing or two the first time you wind it up. Another "good idea" bites the dust...so does that block unless you can get some 10 mm bigserts that will fit the tapped holes and still allow 10mm main bolts to be installed.

What sort of 11 mm bolts were you going to use for main bolts?? Without the factory heat treated bolts and bolt tensioning specs the tension on the bolts would be completely off and the lower end would either be underclamped (and fail) or over clamped (and fail). Tensioning of the main bolts in the correct pattern and to the correct tension is VITAL to make sure the main bearing holes are round. The bolts must be installed and tensioned to the factory tensions to duplicate what was done to the block when the mains were machined. Without the exact tensions and bolts specifiec the mains will not be "round" due to distortion and the engine will fail.

There is not sufficient material in the main web thickness to overdrill the lower crank case holes for additional clearance for 11 mm bolts to allow sufficient oil flow. The main webs will be too thin and crack under load. It might work for awhile but I would not trust it at all personally.

Sorry I was out of town for a few days and did not intercept this plan before you started drilling but I would stop right where you are and figure what to do next. Proceding with 11 mm bolts in those main bolt holes will NOT WORK. I would take the lower crank case apart, clean everything up and figure out how to get bigserts or something to allow the holes to be returned to 10 mm bolt size. That, or have some special studs made that have the 11 mm thread and the shanks turned down to 10 mm to allow the adequate oil flow to the mains and rods. It might be cheaper to find another block.....

Re: Main thread pulled out

Originally Posted by bbob

Do I understand you correctly that you have drilled out the main bolt holes for 11 mm bolts and installed 11 mm timeserts...???

You should have waited until I was back in town, dude....
The oil flow area is the difference in the hole size and the bolt size. The hole is bigger than the bolt so there is room for the oil to flow around the OD of the bolt shank. This is why there are 10 mm bolts in the mains...to allow room for the oil flow around the OD of the bolt. By putting larger 11 mm bolts in the holes you have mostly plugged off the oil supply to the mains. This will NOT work.

What sort of 11 mm bolts were you going to use for main bolts?? .

Yes Bbob you got it right.
Wow Bbob out of the 185 people who have read this thread you were the only one to see that potential problem. I drilled out the holes and installed a 11M head bolt Time-Serts using the 11M head bolt Time-Sert step drill bit which enlarged the factory oversized designed hole considerably.

I can certainly see the problem you point out - I was focusing on the depth and width concerns and did not consider there was a secondary function. I might of figured that out had I drilled and installed the Time-Serts with the halfcase and manifold off. But no, in my attempt to do the job with the halfcase and manifold seal and still on, this critical issue was concealed, out of sight and forgotten and appearently not just by me. And now that you have brought that critical secondary function to my attention (the oil passage ways) I MUST take it all apart to clean out the oil passage ways at the split line from the drilling and tapping fillings that no doubt have worked in there in abundance. Thank you Bbob you sure do know your stuff. It will also be an opportunity to inspect the postioning of the Serts and inspect for crack as they where not recessed much below the split line or surface of the block. I expect none as other Time-Sert appliction they are installed flush with the surface

As for which bolts I was going to use I selected the used 11M N* head bolts which I had on hand they are about 0.60 inch longer than the 10M. The 10M holes was drill out deeper but only to the point the sert could fit in the block and the extra length of the hole need to tap the hole to asure the threads were fully formed in the block to at least the depth of the Tme-Sert (didn't want to cause a break out). The additional extra bolt length (about 1/8 inch) would be reduced from the end of the bolt or a thick washer added. I drilled out the main's holes with the Time-Sert step drill bit which was long enough as was the tap to do the job with the case and manifold still on. (Which since I have to take it all off to clean the oil passage ways out, was no advantage at all and a complete waste)

The stock main bolt hole use to measure about 0.420 ID
The 10M bolt shank measures 0.353 OD
Resulting a space for the oil to flow of 0.067 oil space

The new step drilled whole is now 0.529 ID
The 11M bolt shank measures 0.395 OD
Resulting in a space for the oil to flow of 0.124 oil space

The new holes will have even greater space for oil flow not less. But this is because the halfcase was drilled through with the 11M head bolt Time-Sert step drill bit

Bbob you were right on the money - if the holes in the halfcase were not redrilled and resized the shank of 11M bolt (0.395) would have filled the factory over sized holes (0.420) of the halfcase not that a person is likely to ge them through the half case at the threads of the halfcase are larger (0.430) are slightly larger than the unmodified holes.

The bolt hole area is 1.00 wide, the enlarged holes still leaves 0.471 of material at the thinest area around the holes of the halfcase to carry the load plus much more near by material uneffected by the enlarging and in most places is solid and as I mentioned is 1.00 wide.

Question - with both the 10M and 11M bolts having a 1.5 pitch would tightening be simular to get the same clamping force. I figured (I took a wild gusse) that a reduction of 5 degrees of rotation was resonable to compensate for the head bolts being stiffer even though they are longer by 0.60.

I am finally off work again and will take off the halfcase in the morning weather permitting and see what else I have missed.

Bbob, there is some confussion about what are the latest tightening specs for the head bolts and also for the mains, different numbers are floating around in different location. Could you set the record straight and give the spec with it's issue date. Also to make it easy for everyone to find them when they need them, could you post them in a new thread appropriately titled.

Re: Main thread pulled out

The LCC is going to be weakened substantially with the larger holes in it. The original design of the engine and the main web thickness left little allowance for enlarging the main bolt clearance holes in the LCC without weakening it substantially. It may be fine for limited use but would never live on a full power endurance test without cracking a main web.

I hate to even try to predict a bolt tensioning method. Your guess of using the existing main bolt tensioning procedure and drop the angle 5 degrees is probably a good place to start.....

When the LCC is apart look at the oil flow path into the annulus behind the main bearing carefully to make sure that the oil flow path was not blocked by the timesert insert the way it ended up being installed.

To see what really happened to the oil flow capability you need to look at the area difference between the bolt OD and the hole ID not just the radial dimension of the two.... It still looks like there is plenty with the modified holes as the orginal oil flow path had .0406 square inches per your numbers and the modified setup will have .0972 square inches....but....check my math.